Line fault indicating system



Aug. 24, 1948.

J. S. ASTIN LINE FAULT INDICATING SYSTEM Filed Dec. 29, 1945 Bus Secf/an phase Phat: 2

Busiec flan 2.

Phase 3 WITNESSES:

INVENTOR Jam 65 6: H5 fin.

ATTOR Y Patented Aug. 24, 1948 LINE FAULT INDICATING SYSTEM James S. Aatln, Pittsburgh, Pa., ammo:- to Westinghouae Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 29, 1945, Serial No. 638,566

lly invention relates, generally, to indicating systems and. more particularly, to alarm systems for indicating a grounded phase of a three-phase power system.

On a three-phase ungrounded power system, it is often desirable to provide some method of indicating when a phase accidently becomes grounded. One method which has been utilized is to connect-the actuating coil of a voltage relay in the broken-delta on the secondaryside of potential transformers which are Y-connected .on the primary side with their neutral grounded, When a phase becomes grounded, voltage is developed across the coil of the relay which closes its contact members and sounds an alarm.

Since it usually requires considerable time to locate and remove the ground, itis desirable to be able to silence the alarm and yet leave the circuit in such condition that a subsequent ground on any other bus section will again sound the alarm. One or the objects of my invention is to provide an indicating system capable of performing the foregoing function.

Another object or my invention is to provide a ground indicating system which is automatically restored to normal after the ground is cleared.

A further object .of my invention is to provide a ground indicating system which may be utilized with one or a plurality of sections of a power system.

A more general object at my invention is to provide a ground indicating system which shall be simple and emcient in operation and which may be economically manufactured and installed.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of my invention, relays are so connected to potential transformers that an alarm is sounded when a ground occurs on any one of the conductors of a plurality of sets of conductors and a visual indication of which conductor is grounded is provided. The alarm may be silenced without turning off the visual indication and subsequent ground on any other set of power conductors will sound the alarm.

I' or a fuller understanding of the nature and objects of my invention, reference may be had to the following detailed description, taken in con- Junction with the accompanying drawing, in which the single figure is a diagrammatic view of an indicating system embodying .the principal features of my invention.

Referring to the drawing, the indicating sys- 2 Claims. (Cl. 117-311 tem shown therein is suitable for indicating a ground on either one, or both, of a pair of threephase bus sections designated as bus section I and bus section I. It will be understood that the system may be utilized with any desired number of bus sections or sets of power conductors by providing additional apparatus similar to that illustrated.

The apparatus required for bus section I comprises a set of potential transformers PTI. A voltage relay VI, an auxiliary relay VXI, a pushbutton switch PBI, indicating lamp I, 2, 3, XLI and LI and an alarm A which may be a buzzer or hell or other suitable signalling device.

The apparatus for the bus section 2 is similar to that for the bus section I and comprises a set of potential transformers PTI, a voltage relay V2, an auxiliary relay VX2, a push-button switch PB! and indicating lamps 2|, 22, II, X1112 and L2. The alarm device A is common for both bus sections and need not be duplicated.

As shown, the primary windings of the potential transformers PTI are Y-connected to the power conductors of bus section I, the neutral of the Y-connected transformers being grounded. The secondary winding of the potential transformers are delta-connected with the actuating coil of the voltage relay VI connected in the broken delta through normally closed contact members II of the auxiliary relay VXI. The indicating lamps I, 2 and 3 are so connected across the secondary windings for phases I, 2 and 3 that the three lamps burn with equal brilliance under normal conditions. However, when a ground occurs on one of the phases, the lamp corresponding to that phase becomes dark, while the remaining two burn with increased brilliance, thereby providing an indication of which phase is rounded.

Furthermore, when a ground occurs phase, the actuating coil of the relay VI becomes energized, thereby closing its contact members to energize the alarm device A. The operator can tell which bus section and which phase of the bus section is grounded by noting the condition members I2 which are closed when the actuating coil of the relay is energized.

onany' departing from the spirit and .scope thereof, it i is intended that all matter contained in the loreauxiliary relay VX! which returns to its original position. It a ground occurs on another bus-section, such as bus section 2, before the auxiliary relay Vxi a deenergized, the alarm A will be sounded by the operation of the relay V2 in a manner similar to the operation oi the relay VI on the bus section I.

The alarm A may be silenced by closing the push-button switch PBZ which causes the operation of the relay VX2 in the same manner as the relay VXI. Likewise, a ground occurring on any other bus section provided with-the indicating apparatus will cause the operation of the'alarm device A.

If it is desired to provide a visual indication at some remote point as to which bus section is go grounded after the alarm device has. been silenced, the indicating lamp Ll may be energized through contact members It or the auxiliary relay VXI, or the indicating lamp XL! may-be connected in parallel-circuit relation with the; 35., actuating coil of the auxiliary relay VXI in the, manner shown. Ii desired, both lamps may be.

utilized and located at two diflerent points.

-These lamps will continue to burn until the ground is removed from the power conductor. so

Thus, by providing similar lamps for each bus section, visual indications. of the condition of each bus section may be provided at any desired location.

From the foregoing description, it is apparent 5 that I have provided a system suitable for indicating a ground on any power conductor of a plurality of sets of power conductors, and for identifying the particular power conductor involved.

The system permits the signalling or alarm device 4 the alarm device regardless of. whetheror not the first ground has been cleared. The system is automatically restored to normal upon the clearance of the ground, without depending upon the operator to reset the apparatus.

Since numerous changes may be made in the 2,115,027

above-described construction and diflerent embodiments oi the invention may be made without oing description or shown in the accompanyin drawing shall be considered as illustrative and notinalimitingsense. g M

I claim as my invention:

, 1. In an indicating system. in combination. a

set or three-phase power conductors. potential transformers havin primary windings connecmd to said power conductors, a voltage relay having an actuating coil connected to the secondary windings of said transformers to be responsive to a ground on one of said power conductors, an alarm device energized through the contact members of said relay, an auxiliary relay for controlling the operation of said voltage relay, manually operable means for controlling the energization of said auxiliary relay by said potential transformers, and contact members on said auxiliary relay for establishing a holding circuit or the auxiliary relay, said holding circuit being deenergized by the'removal of. the ground from said power conductor.

2.11; an indicating system, in combination, a plurality of sets of three-phase power conductors, alfrsetof potential transformers for each set of power-conductors, said transformers having primary windings connected to the power conductors, a voltage relay tor each set of transformers, said relays having their actuating coils connected to the secondary windings 01' said transformers to be responsive'to grounds on the powerconductors, an alarm device energized through the contact members of said relays, anauxiliary relay for controlling the operation oi.- each voltage relay, manually operable means for controlling the energization of each, auxiliary relay, and holding means for each auxiliary relay,said relays being automatically deenergized by the removal of the ground from their respective power conductors.

JAMES S. AS'I'IN.-

' REFERENCES CITED UNITED STATES PATENTS- Number Name Date 1,300,546 Armstrong Apr. 15, 1919 Leonard Apr. 26, 1938 2,275,883 Bany Mar. 10, 1942 2,368,471 Horan Jan. 30, 1945 

